A typical prior art hand held paint spray gun includes a gun body having a nozzle assembly mounted on one end and having a handle depending from adjacent an opposite end. A trigger is attached to the gun body to pivot towards and away from the handle. When an operator holds the gun by the handle and squeezes the trigger, an air valve is opened and then a valve needle is moved to open a fluid valve. The air valve supplies any air required for atomization and for shaping the spray pattern. If the trigger is only partially squeezed, the fluid valve may be only partially opened to permit the operator to apply a lighter coating, for example, for feathering when touching up a coating. The spray gun also includes an adjustable stop which limits trigger travel to adjust the maximum paint flow from the gun when the trigger is fully squeezed. Trigger travel may be limited either by a direct adjustable stop for the trigger or indirectly by limiting the maximum linear movement of the valve needle.
Fluid flow is typically adjusted by rotating a knob on the back of the gun body. When the fully triggered fluid flow from a spray gun is adjusted to less than the maximum flow the trigger will stop short of the spray gun handle when it is squeezed. In some cases, if an operator squeezes the trigger too hard, the gun will be damaged. In order to reduce the risk of damage to the gun from squeezing the trigger too hard, the gun components must be designed to be stronger than is required for normal operation. The stronger gun components add weight to the gun, which in turn will increase operator fatigue. It has not been possible to construct prior art commercial quality spray guns from lighter weight materials such as plastics without risk of failure.